Tympan-sheet.



PATENTED AUG. 18, 1908. J. FRASER.

-TYMPAN SHEET. APPLICATION FILED MAY 13,1907.

anuenior;

UNITED STATES PATENT OFFIGE- JOHN FRASER, OF BOSTON, MASSACHUSETTS, ASSIGNOR TO HIMSELF AND WILLIAM A. TAR- BE'IT, OOPARTNERS UNDER THE FIRM-NAME OF 'IARBETT AND FRASER.

TYMPAN-SHEE T.

Specification of Letters Patent.

Patented Aug. 18, 1908.

Application filed May 13, 1907. Serial No. 373,338.

T 0 all whom it may concern:

Be it known that I, JOHN FRASER, citizen of the United States, residing at Boston, in the county of Suffolk and State of Massachusetts, have invented certain new and useful Improvements in TympanSheets, of which the following is a specification.

My invention relates to tympan sheets for impression cylinders and the like, and more particularly has for its object to provide a construction whereby the said tympan sheet may be applied to the operative surface of the impression cylinder in a manner permitting the said sheet to be maintained tightly stretched over said surface.

More particularly my invention is made use of in making repairs to impression cylinders, or other cylindrical machine elements, whose operative surfaces have become worn or injured in use. In many cases such injured surfaces may be trued up merely by lathe turning, but in some cases the diminution in the diameter of the impression cylinder caused by the removal of material incident to such a process may render the same unavail able for future use. Insuch a case it is necessary to first build up the surface of the said cylinder before truing up, and an obvious method of doing this is by attaching to the said operative surface a metal tympan sheet, conforming to the curvature of said surface and having the necessary thickness. Hitherto, so far as I am informed, a tympan sheet so applied to an impression cylinder surface has been attached thereto by screws, rivets, or the like, and although said sheet may be initially securely attached thereby, it will in time loosen up by use.

To remedy this my invention has for its purpose to provide a construction whereby a tympan sheet may be initially tightly stretched over the surface of the impressioncylinder to which it is applied, and embodying means whereby said sheet may be again tightened upon said surface in case it becomes loosened by use.

Referring to the accompanying drawings which form a part of this specification, and in which similar reference numerals indicate corresponding parts in all the figures, Figure 1 shows a perspective view of one end of an impression cylinder having a tympan sheet applied thereto in a manner embodying my invention the end of said cylinder nearer the observer being cut away in order to more In Fig. 1 is shown one end of an impression cylinder, mounted. on a shaft 1, by means of which the said cylinder may be positioned in the printing press. The necessary rigidity is given to the cylindrical operative surface 2 of said cylinder by means of the spoked hubs 3 through which shaft 1 passes. The end of said cylinder is preferably solid as shown at 4 in said Fig. 1.

As shown in Figs. 1 and 2 the operative surface 2 of the impression cylinder comprises slightly more than thelower half of the circumference of said cylinder, there being a break on either side of the operative surface forming longitudinal slits 5 opening into the interior of the said cylinder as ap pears in Figs. 1 and 2. In some cases however said longitudinal slits or openings 5 may be in part or wholly closed, as in Fig. 3, by means of a web 6 lying inside the circumference of the cylinder and extending for a greater or less part of the length of the same.

The tympan sheet 7 is attached to the operative surface of the impression cylinder 11 in the following manner. Said operative surface, if necessary, is first trued up by machining, enough material being removed therefrom to make room for that to be supplied by the tympan sheet. Said sheet, preferably of brass, and of the required dimensions is curved to conform to the curvature of the operative surface, prepared as above, and is fastened at one end to one edge, preferably the gripper edge of the same by means of screws 8, or in any other appropriate manner.

The circumferential length of the tympan sheet with relation to that of the operative surface is such that the free end of said sheet overlaps the other, or tail, edge of the operative surface, and the terminal portion of said free end is preferably bent radially inward for a short distance forming a lip 9, as shown.

To the free end of the sheet, and preferably engaging the lip 9, is attached a guide iron preferably consisting of a piece of angle iron having a length equivalent to the breadth contact is usually found to be at the free end of said sheet. Said guide iron 10 comprises the of said guiding leg.

sheet attaching leg 10*, having the free end of the sheet engaging one surface, while the other, or unengaged surface lies adjacent to the radial portion 17 of the tail edge, and the guiding leg 10, which presents a guide surface extending from the sheet attaching leg in the direction of the fixed end of said tympan sheet; that is, in a downward direction as shown in Fig. 2.

Engaging either or both the lip 9 or the sheet attaching leg of the guide iron are the straining means, preferably comprising the set screws 13 bearing against the radial portion 17 of the tail edge of the operative surface, or against some other convenient part of the impression cylinder. Lying closely adjacent to the guiding surface of the guide iron are the guiding means adapted to cooperate with. the said guide surface in preventing the rotation of the tightening devices. Said. means preferably consist of the pins 12 set into the spokes of the impression cylinder as shown, in Fig. 2, and alined in substantial parallelism with said guiding surface.

When the set screws 13 are first screwed up it will be seen that the force exerted there by, being out of alinement with the resistance offered by the tympan sheet, will produce a rotation of the lip 9, with the devices at tached thereto, in a rigl'it handed. direction, as shown in Fig. 2, about'the corner of said bent over lip 9 as an approximate center. As aresult of such rotation the guiding leg 10 of the guide iron 10 will be brought immediately into contact with pins 12, and the re sistance resulting from such contact will prevent any further rotation of said tightening devices about the said corner of the lip 9. As the screwing up of the set screws 13 continues pins 12 will operate to prevent the further rotation of the tightening devices, and'thus tact, taken about the same point.

insures that the force exerted by screwing up the set screws will be applied to the free end of the tympan sheet for'the purpose of drawing the same tightly over the" operative surface of the impression cylinder.

An analysis of the causes leading to this result shows that as the tightening of the set screws 13 proceeds, the tightening devices will eventually assume a statical condition in which there is a moment, due the tension of the sheet, and tending to rotate the tightening devices about the point of the set screws 13 as a center, which is counterbalanced by the moment of the force with which the guiding leg of the guide iron and pins 12 con- From the above analysis it will appear that in order to reduce the intensity of the force with which the guiding leg and the pins 12 contact it is desirable that the pointof such contact be as remote as possible from the points of said set screws, and as a matter of fact such point of It is however apparent that a moment adapted to counterbalance the moment set up by the tension in the tympan sheet will theoretically be secured whenever said pins 12 are in contact with the lower surface of the guiding leg, at a point lying to the right of a plane perpendicular to said guiding leg and passing through the point of set screw 13, or, should the .pins 12 be arranged to contact with the upper surface of said guiding leg, at a point lying to the left of said plane. That is, the possible range of the point of contact between said guiding leg and the pins 12 may be said to lie between a plane passing through the unengaged surface of the sheet attaching leg of the guide iron, that is, that surface lying adjacent the tail edge 17, and the end of the guiding leg of the said guide iron.

- I am aware that tightening means have been hitherto employed in analogous situa tions which somewhat resemble in generalappearance and operation the construction of the applicant. In such cases however, the guiding leg of the guide iron extends from the sheet attaching leg of the same in a direction away from the fixed end of the tympan sheet, and not towards the same as in the construction of the applicant. Furthermore it is necessary in such cases that the means for preventing the rotation of the tightening devices extend in the same direction as, and beyond the guiding leg of the guide iron for a distance dependent upon the amount of tightening movement required, and also that the said means be adapted to contact with said guide iron on its outer surface. Such prior constructions therefore require for their installation a space having an angular extent proportioned to the sum of the lengths of the guiding leg and of the means adapted to contact with the same. In my construction, however, the angular extent of thespace required for the installation of the tightening devices is substantially dependent of the length of the guide surface alone. Thus for an equal adjustment capacity my construction requires a space of much less angular extent than those heretofore employed. At the same time in my construction the guiding leg of the guide iron and the means engaging the said surface, unlike the prior constructions, are substantially concealed, lying as they do radially inward with respect to the free end of the tympan sheet. Being therefore out of sight in my construction these parts are less obtrusive in the matter of appearance, and afford less opportunity for the lodgment of dirt or refuse, as well as presenting less of an obstacle to the manipulation of a brush or swab when it is desired to clean up that portion of the impression cylfee use it may be readily retightened by screwing up still further the set screws, and the process may be repeated until the sheet has elongated to such an extent that the guiding leg of the guide iron no longer contacts with the pins 12. In such case the sheet may be shortened, and the angle iron reattached as before in a new position wherein its guiding leg is again in contact with the pins 12, and operates as above described.

In some cases, especially Where the presser roll is of the type shown in Fig. 3, it is preferable to substitute in place of one continuous length of angle iron, a number of short lengths of the same individually applied to the free end of the sheet in the manner above described in connection with the cases where the single length is used. In such cases preferably each angle iron is provided with straining means, preferably arranged and operating in the manner heretofore described.- Furthermore in such cases it is preferable to cut in the web 6 holes or slits into which the guiding legs of the series of angle irons may be introduced, and which will cooperate therewith in preventing the rotation of the tightening devices, when they are put into operation, in a manner analogous to that described above in connection with Figs. 1 and 2. In said Fig. 3 is also shown a modificathm.of the manner in which the guide iron and straining means may be applied to the end of the tympan sheet. Instead of the bent over hp 9 an angle iron 16 may be attached to the free end of said sheet by screws 15, and to the free leg of this angle iron may be fastened, by rivets 14, one leg of a guide iron 10. The straining means as before are preferably set screws 13 engaging either or both the contacting legs of angle and guide iron, the whole operating as described above more particularly in connection with Figs. 1 and 2.

Having described my invention, what I claim is:

1. In printing machines, in combination with an impression cylinder, a tympan sheet fitting over the operative surface of said impression cylinder and fixed at one end with respect thereto, tightening devices comprising, a guide iron secured to said sheet at its free end, and having a guide surface lying substantially parallel to the said free end of the tympan sheet, and extending in the direction of the fixed end of the same, and straining means engaging said guide iron, bearing against said impression cylinder, and adapted to impart a tightening movement to the said guide iron, and means contacting with said guide surface at that portion there of lying between a radial plane passing through the point of contact of the straining means with the impression cylinder and the end of said guide surface lying nearer the fixed end of the tympan sheet, and adapted to cooperate with said guide surface in preventing the rotation of the tightening devices.

2. In printing machines, in combination with an impression cylinder, a tympan sheet fitting over the operative surface of said im pression cylinder and fixed at one end with respect thereto, tightening devices comprising, a guide iron having a sheet attaching leg, one surface of said leg being in engagement with the terminal portion of the free end of the tympan sheet, and the other, or unengaged surface of said leg lying opposite and adjacent to the tail edge of the impression cylinder, and a guiding leg lying substantially parallel to the free end of the tympan sheet, and extending in the direction of the fixed end of the same, straining means engaging said guide iron bearing against said impression cylinder, and adapted to impart a tightening movement to the said guide iron, and means engaging said guiding leg at that portion thereof included between a plane passing through the unengaged surface of the sheet attaching leg, and the end of said guide surface lying towards the fixed end of the tympan sheet, and adapted to cooperate with said guide surface in preventing the rotation of the tightening devices.

In testimony whereof I affix my signature in presence of two witnesses.

JOHN FRASER.

Witnesses:

NATHAN B. DAY, HENRY Y. WIGGIN. 

